1. Field of the Invention
The present invention relates generally to a slide fastener for use on a bag, for example, made of a nonwoven sheet material to open and close an opening therein, and more particularly to such a slide fastener having stringer tapes made of the same materials as the bag and carrying rows of coupling elements sewn to the inner longitudinal edges of the tapes.
2. Prior Art
Known slide fasteners for attachment to bags of nonwoven sheet material comprise stringer tapes made of a nonwoven sheet material and supporting rows of coupling elements sewn directly to their inner longitudinal edges thereof. Since the stringer tapes are perforated by the sewing needle, they become weak in mechanical strength. When such a slide fastener is subjected to transverse forces tending to pull the stringer tapes laterally apart, the stringer tapes are likely to be torn apart along their respective perforated longitudinal edges before the rows of coupling elements are disengaged from each other. Further, the stringer tapes of nonwoven sheet material are liable to be damaged due to frictional engagement with a slider during use of the slide fastener. Throughout the specification and the claims, the term "nonwoven sheet material" is used to refer to such a material as paper, nonwoven fabric, felt or thermoplastic synthetic resin film, but to exclude woven or knitted fabric.